[Closed] Boeing X51 scramjet

Cool plane, reminds me why I did an aeronautics degree 🙂

Potent weapon: potentially, and certainly the US government funding includes that possibility. I very much doubt the complete test data will be in the public domain!

Joke? No.

Will anything (civil) come of it? Possibly, there's certainly a demand for sub 5 hour flights to Australia, for example.

Will anything (civil) come of it? Possibly, there's certainly a demand for sub 5 hour flights to Australia, for example.

I suspect the 50/50 reliability might be a factor for paying customers!

In my sci fi minds eye I can imagine (and am craving) some sort of unmanned delivery vehicle that flies from a launch pad to a station and back and forth over thousands of miles. And yeah the civil the applications will be incredible but I guess that is a long way away due to H&S testing that will need to be done lol.

I think we'll see a manned fighter jet using scramjet engines in the near future though.

Am I right in thinking there are no manned aircraft currently existing that use scramjet as opposed to ramjet?

I suspect the 50/50 reliability might be a factor for paying customers!

Pfft, cowards.

Am I right in thinking there are no manned aircraft currently existing that use scramjet as opposed to ramjet?

Well, as the X-51 is the proof-of-concept prototype, I think the answer to that question is pretty obvious! 😀
To my knowledge, no manned aircraft has used any type of ramjet technology. Rocket propelled, yes, but I don't recall ever reading about any manned ramjet aircraft.
I'll just go and do a wiki search.
[edit] just had a shufti, and there was a proposed replacement for the U2 in 1959, the Convair Kingfish, that was supposed to get up to Mach 4, powered by two P&W ramjets, but the CIA dropped it because of cost over-runs and the continuing success of the U2. Which still flies, having outlasted the SR71, which is what the CIA went for in the end, because Lockeed had the Skunk Works, which were totally secure, and Convair didn't.

no manned aircraft has used any type of ramjet technology

SR-71? IIRC at operating speed the J58 engines operated as ramjets.

Andy

The blackbird was pretty much a ramjet when supersonic with the intake cones?

You're right about the P&W engines being effectively ramjets:

The air inlets had to allow cruising at over Mach 3.2, yet keep air flowing into the engines at the initial subsonic speeds. At the front of each inlet was a pointed, movable cone called a "spike" that was locked in its full forward position on the ground and during subsonic flight. As the aircraft accelerated past Mach 1.6, an internal jackscrew withdrew the spike up to 26 inches (66 cm) inwards,[20] as directed by an analog air inlet computer that took into account pitot-static, pitch, roll, yaw, and angle of attack. By moving, the spike tip would withdraw the shock wave, riding on it closer to the inlet cowling until it just touched slightly inside the cowling lip. This position reflected the spike shock-wave repeatedly between the spike centerbody and the inlet inner cowl sides, and minimized shock-wave spillage, which caused turbulence over the outer nacelle and wing. This maintained shock pressures while slowing the air until a Mach 1 shock wave formed in front of the engine compressor.[21]

Operation of the air inlets and air flow patterns through the J58
The backside of this "normal" shock wave was subsonic air for ingestion into the engine compressor. This capture of the Mach 1 shock wave within the inlet was called "Starting the Inlet". Tremendous pressures would be built up inside the inlet and in front of the compressor face. Bleed tubes and bypass doors were designed into the inlet and engine nacelles to handle some of this pressure and to position the final shock to allow the inlet to remain "started". Air compressed by the inlet/shockwave interaction was diverted directly into the afterburner to be mixed and burned. [b]This configuration is essentially a ramjet and provides up to 70% of the aircraft's thrust at higher Mach numbers.[/b][citation needed] Ben Rich, who designed the inlets at the Skunkworks, often referred to the engine compressors as "pumps to keep the inlets alive"; he sized the inlets for Mach 3.2 cruise, the aircraft's most efficient speed.[22] The additional thrust refers to the reduction of engine power required to compress the airflow; the SR-71 was more fuel-efficient at higher speeds, in terms of pounds burned per nautical mile traveled. During one mission, SR-71 pilot Brian Shul flew faster than usual for some time to avoid multiple interception attempts; afterwards, it was discovered that this had reduced fuel consumption.[23]

In the early years of operation, the analog computers would not always keep up with rapidly changing flight environmental inputs. If internal pressures became too great and the spike was incorrectly positioned, the shock wave would suddenly blow out the front of the inlet, called an "Inlet Unstart." During an unstart, air flow through the engine compressor immediately stopped, thrust dropped, and exhaust gas temperatures rose. The remaining engine's asymmetrical thrust would cause the aircraft to yaw violently to one side. SAS, autopilot, and manual control inputs would fight the yawing, but often the extreme off-angle would reduce airflow in the opposite engine and stimulate "sympathetic stalls". This generated a rapid counter-yawing, often coupled with loud "banging" noises, and a rough ride during which crews' helmets would sometimes strike their cockpit canopies.[24] One response to a single unstart was unstarting both inlets to prevent yawing, then restarting them both.[25] Lockheed later installed an electronic control to detect unstart conditions and perform this reset action without pilot intervention.[26] Beginning in 1980, the analog inlet control system was replaced by a digital system, which reduced unstart instances.

I checked my facts before posting and got a bit carried away reading that article.

A good SR-71 story, written by a former pilot (Brian Shul)

There were a lot of things we couldn’t do in an SR-71, but we were the fastest guys on the block and loved reminding our fellow aviators of this fact. People often asked us if, because of this fact, it was fun to fly the jet. Fun would not be the first word I would use to describe flying this plane. Intense, maybe. Even cerebral. But there was one day in our Sled experience when we would have to say that it was pure fun to be the fastest guys out there, at least for a moment.

It occurred when Walt and I were flying our final training sortie. We needed 100 hours in the jet to complete our training and attain Mission Ready status. Somewhere over Colorado we had passed the century mark. We had made the turn in Arizona and the jet was performing flawlessly. My gauges were wired in the front seat and we were starting to feel pretty good about ourselves, not only because we would soon be flying real missions but because we had gained a great deal of confidence in the plane in the past ten months. Ripping across the barren deserts 80,000 feet below us, I could already see the coast of California from the Arizona border. I was, finally, after many humbling months of simulators and study, ahead of the jet. I was beginning to feel a bit sorry for Walter in the back seat.

There he was, with no really good view of the incredible sights before us, tasked with monitoring four different radios. This was good practice for him for when we began flying real missions, when a priority transmission from headquarters could be vital. It had been difficult, too, for me to relinquish control of the radios, as during my entire flying career I had controlled my own transmissions. But it was part of the division of duties in this plane and I had adjusted to it. I still insisted on talking on the radio while we were on the ground, however. Walt was so good at many things, but he couldn’t match my expertise at sounding smooth on the radios, a skill that had been honed sharply with years in fighter squadrons where the slightest radio miscue was grounds for beheading. He understood that and allowed me that luxury. Just to get a sense of what Walt had to contend with, I pulled the radio toggle switches and monitored the frequencies along with him.

The predominant radio chatter was from Los Angeles Center, far below us, controlling daily traffic in their sector. While they had us on their scope (albeit briefly), we were in uncontrolled airspace and normally would not talk to them unless we needed to descend into their airspace. We listened as the shaky voice of a lone Cessna pilot asked Center for a readout of his ground speed. Center replied: “November Charlie 175, I’m showing you at ninety knots on the ground.”

Now the thing to understand about Center controllers, was that whether they were talking to a rookie pilot in a Cessna, or to Air Force One, they always spoke in the exact same, calm, deep, professional, tone that made one feel important. I referred to it as the ” Houston Center voice.” I have always felt that after years of seeing documentaries on this country’s space program and listening to the calm and distinct voice of the Houston controllers, that all other controllers since then wanted to sound like that, and that they basically did. And it didn’t matter what sector of the country we would be flying in, it always seemed like the same guy was talking. Over the years that tone of voice had become somewhat of a comforting sound to pilots everywhere. Conversely, over the years, pilots always wanted to ensure that, when transmitting, they sounded like Chuck Yeager, or at least like John Wayne. Better to die than sound bad on the radios. Just moments after the Cessna’s inquiry, a Twin Beech piped up on frequency, in a rather superior tone, asking for his ground speed. “I have you at one hundred and twenty-five knots of ground speed.”

Boy, I thought, the Beechcraft really must think he is dazzling his Cessna brethren. Then, out of the blue, a navy F-18 pilot out of NAS Lemoore came up on frequency. You knew right away it was a Navy jock because he sounded very cool on the radios. “Center, Dusty 52 ground speed check”. Before Center could reply, I’m thinking to myself, hey, Dusty 52 has a ground speed indicator in that million-dollar cockpit, so why is he asking Center for a readout? Then I got it, ol’ Dusty here is making sure that every bug smasher from Mount Whitney to the Mojave knows what true speed is. He’s the fastest dude in the valley today, and he just wants everyone to know how much fun he is having in his new Hornet. And the reply, always with that same, calm, voice, with more distinct alliteration than emotion: “Dusty 52, Center, we have you at 620 on the ground.”

And I thought to myself, is this a ripe situation, or what? As my hand instinctively reached for the mic button, I had to remind myself that Walt was in control of the radios. Still, I thought, it must be done – in mere seconds we’ll be out of the sector and the opportunity will be lost. That Hornet must die, and die now. I thought about all of our Sim training and how important it was that we developed well as a crew and knew that to jump in on the radios now would destroy the integrity of all that we had worked toward becoming. I was torn. Somewhere, 13 miles above Arizona, there was a pilot screaming inside his space helmet. Then, I heard it. The click of the mic button from the back seat. That was the very moment that I knew Walter and I had become a crew. Very professionally, and with no emotion, Walter spoke: “Los Angeles Center, Aspen 20, can you give us a ground speed check?” There was no hesitation, and the replay came as if was an everyday request. “Aspen 20, I show you at one thousand eight hundred and forty-two knots, across the ground.”

I think it was the forty-two knots that I liked the best, so accurate and proud was Center to deliver that information without hesitation, and you just knew he was smiling. But the precise point at which I knew that Walt and I were going to be really good friends for a long time was when he keyed the mic once again to say, in his most fighter-pilot-like voice: “Ah, Center, much thanks, we’re showing closer to nineteen hundred on the money.” For a moment Walter was a god. And we finally heard a little crack in the armor of the Houston Center voice, when L.A.came back with, “Roger that Aspen, Your equipment is probably more accurate than ours. You boys have a good one.”

It all had lasted for just moments, but in that short, memorable sprint across the southwest, the Navy had been flamed, all mortal airplanes on freq were forced to bow before the King of Speed, and more importantly, Walter and I had crossed the threshold of being a crew. A fine day’s work. We never heard another transmission on that frequency all the way to the coast. For just one day, it truly was fun being the fastest guys out there.

That's one of my favourite SR-71 stories, along with one where a load of pilots are asking air traffic control for permission to fly a various altitudes, it turns into an altitude willy waving contest, so the blackbird navigator comes on with
SR71 'SR71 to tower, request permission to fly at 60,000 feet?'
Tower 'Yeah, sure. If you think you can get that high!'
'Roger that tower. Descending to 60,000 feet'

Hehe

Thank you for the two Blackbird stories, I [i]never[/i] get tired of reading those, and they always raise a smile. 😀

I love that story, never fails to make me chuckle.

Priceless. Reminds me somewhat of this:

aircraft carrier (U.S.S. Abraham Lincoln) and Canadian authorities
off the coast of Newfoundland in October, 1995. (The radio
conversation was released by the Chief of Naval Operations on
10/10/95 authorized by the Freedom of Information Act.)

Canadians: Please divert your course 15 degrees to the South to
avoid collision.

Americans: Recommend you divert your course 15 degrees to the
North to avoid a collision.

Canadians: Negative. You will have to divert your course 15
degrees to the South to avoid a collision.

Americans: This is the Captain of a US Navy ship. I say again,
divert YOUR course.

Canadians: No, I say again, you divert YOUR course.

Americans: THIS IS THE AIRCRAFT CARRIER USS LINCOLN, THE SECOND
LARGEST SHIP IN THE UNITED STATES' ATLANTIC FLEET. WE ARE
ACCOMPANIED BY THREE DESTROYERS, THREE CRUISERS AND NUMEROUS
SUPPORT VESSELS. I DEMAND THAT YOU CHANGE YOUR COURSE 15 DEGREES
NORTH--I SAY AGAIN, THAT'S ONE FIVE DEGREES NORTH--OR
COUNTER-MEASURES WILL BE UNDERTAKEN TO ENSURE THE SAFETY OF THIS SHIP.

Canadians: This is a lighthouse. Your call.

Possibly a fake but...

Iranian Air Defense Site: ‘Unknown aircraft you are in Iranian airspace. Identify yourself.’

Aircraft: ‘This is a United States aircraft. I am in Iraqi airspace.’

Air Defense Site: ‘You are in Iranian airspace. If you do not depart our airspace we will launch interceptor aircraft!’

Aircraft: ‘This is a United States Marine Corps FA-18 fighter. Send ‘em up, I’ll wait!’

Air Defense Site: ( …. total silence)

I suspect the 50/50 reliability might be a factor for paying customers!

Might confuse Ryanairs pricing as well,
"can we charge them extra to survive?, to be sure we can, call it a landing conversion charge"

I think we'll see a manned fighter jet using scramjet engines in the near future though.

seriously doubt that the air force is moving towards drones/unmanned for many reasons. making a reliable high mach aircraft will be much easier if you dont need things like life support, ejection seats etc.

also didn't the US announce a few years ago they are looking at systems with the capability to attack anywhere on earth within 90min. scramjets are the tech to make this happen.

The sheer, insane cost of ever more sophisticated fighter and air support aircraft pretty much dictates that UAV's will become more sophisticated, and the need for billion dollar fighters will diminish dramatically. It's already happening with the Reaper and Predator drones, and the stealth drone we're developing. Another five-ten years, and I'll bet that manned fighters will be an anacronism. Most of the fighters the Americans are using are thirty-plus years old!
From Defense Industry Review:

The current US Air Force fleet, whose planes are more than 23 years old on average, is the oldest in USAF history. It won’t keep that title for very long. Many transport aircraft and aerial refueling tankers are more than 40 years old – and under current plans, some may be as many as 70-80 years old before they retire. Since the price for next-generation planes has risen faster than inflation, average aircraft age will climb even if the US military gets every plane it asks for in its future plans. Nor is the USA the only country facing this problem.

The B-52 has been in service since 1955! It's 57 years old, for Christ's Sake! The F-15 Eagle is 36 years old.

anywhere on earth within 90min. scramjets are the tech to make this happen.

Yeah it's current design is essentially a mach 8 payload delivery system. I suppose the closest thing to exist previously is the infamous v series payload delivery rockets used in the second world war like the doodle bug. Just much much much faster and probably much scarier.

and the need for billion dollar fighters will diminish dramatically.

Yes this is an inevitability to a degree, but I would argue that there will always be pilots. Pilots trained specially to shoot down combat drones, pilots to fly high security missions that need the flexibility and reliability that an unmanned drone cannot provide. We're a long way off computer systems that can make the decisions required in a war zone quickly enough, reliably enough and with the clarity of mind and instant moral decisions that an active pilot makes in a war zone.